There are provisions in the license agreement for you to have your program on two computers at any one time, such as a desktop and a laptop at the same time. They will activate just fine. The idea is, though, that you should only have one version open at any one time.

As one wag on this forum pointed out there isn't any way Adobe can know if you're using the same application on different computers at the same time (at least not that we know about), but it comes down to your ethical position as to whether you wish to be bound by the legal agreement you made on installation.